In the past various attempts have been made to store energy in a steam power plant in order to use it during certain operational conditions.
One attempt suggests a steam power having, parallel to the low pressure preheater passage, a heat reservoir, which is loaded with preheated condensate in weak-load times. This preheated condensate is taken from the heat reservoir for generating peak-load and inserted downstream of the preheater passage into the condensate line and the feed water tank, respectively. Thus it is possible to quickly control the power generation of the power plant in a wide range without significantly having to change the heating output of the boiler of the steam generator. A steam power plant equipped according to embodiments of the invention can thus be operated with bigger load modifications and also provide more control energy.
In another attempt, a steam power plant has, parallel to the low-pressure passage, a heat reservoir which is loaded with preheated condensate in weak-load times. This preheated condensate is taken from the heat reservoir for generating peak-load and inserted downstream of the low-pressure preheater passage into the condensate line and the feed water tank, respectively. An additional heat exchanger is provided to increase the temperature of the hot water sent to the storage. Thus it is possible to quickly control the power generation of the power plant in a wide range without significantly having to change the heating output of the boiler of the steam generator. A steam power plant equipped according to embodiments of the invention can thus be operated with bigger load modifications and also provide more control energy.
In yet another attempt, the integration of hot water energy storage is parallel to the HP feed water preheaters. In this case the storage is at higher temperatures and pressures than in previous attempts mentioned before.
In yet another attempt, a method involving extracting a portion of a steam mass flow from a boiler connected to a water-steam circuit of a steam turbine into an external storage. The steam is released from the external storage and supplied to the steam turbine process when needed. The steam is extracted into the external storage, when the power plant is operated at partial load or when a rapid power reduction is required. The steam turbine is operated in modified variable pressure, and the boiler is filled with the steam while the steam is released from the external storage. Here, during charging the storage is fed by steam from the boiler.
For power plants, where no storage is already installed, one of the above attempts may provide the best solutions. But when a power plant has already a steam storage installed but not dedicated to use it to provide additional power, it is the most cost-effective solution to integrate the existing steam storage in a different way.